JPH0359921A - Vacuum valve - Google Patents

Abstract

PURPOSE:To prevent cracks from being generated at the soldering portion of a bellows with a moveable shaft by mechanical impact vibration by providing the moveable shaft with a collar portion by means of integral molding and hermetically joining one end of the bellows to one end face of the collar portion. CONSTITUTION:A moveable shaft 14 connected to an electrode 4b and extending downward comprises a collar portion 14a formed at its center portion and extending in its radial direction, and a bellows 8 is engaged at one end with the lower end face 14b of the collar portion 14a, and the shaft 14 further extends downward and is guided to the outside. The diameter of the collar portion 14a is roughly the same as that of a conventional bellose cover. In this case, the lower end face 14b of the collar portion 14a can be easily made with accuracy by a mechanical process. Since burr or waviness will not be generated by press punching, there is no need for a thick solder layer to be formed at the soldering portion of the bellose 8 with the lower end face 14b of the collar portion 14a, nor a recessed portion or void that associates the thick solder layer to be provided. A long life vacuum valve of high reliability in its life relating to switching is thus obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a vacuum valve, and particularly to a structure of a vacuum valve with improved reliability in opening and closing life.

(Prior Art) As is well known, a vacuum valve generally has a pair of electrodes that can be moved toward and away from the inside of a vacuum container with an internal pressure of 1×1 O−2 Pa or less, which is an insulating container hermetically sealed with an end plate. It is composed of FIG. 3 shows a conventional vacuum valve 1, in which a pair of electrodes 4a and 4b are provided inside a vacuum container in which both ends of an insulating container 2 are sealed with end plates 3a and 3b.
A fixed shaft 5 is connected to the end plate 3a, passing through the end plate 3a in an airtight manner and protruding to the outside to form an electric circuit. A movable shaft 6 is connected to the other electrode 4b, and protrudes outward through a bellows cover 7 and further through a bellows 8 to form an electric path.
The center hole is inserted to maintain airtightness. Further, the other end of the bellows 8 is airtightly connected to the end plate 3b.

9 is a shield, and the electrode 4a when switching current.

The bellows cover 7 prevents the interior of the insulating container 2 from being contaminated by metal vapor generated from the bellows 8, and prevents this metal vapor from adhering to the bellows 8. Note that these parts are connected by brazing using noble metal solder.

(Problem to be solved by the invention) Recently, there has been a demand for vacuum valves with a long opening/closing life, and in particular, vacuum valves for contactors are required to have a long life of 5 million cycles. There have been cases where this has occurred. Normally, the opening/closing life of a vacuum valve is controlled by the mechanical durability of the bellows. For this reason, as a distant relative of ultra-long life, methods that have been used up until now include increasing the number of bellows, using larger bellows to alleviate the stress exerted by each bellows, and using materials with higher yield strength. Generally, methods were adopted to deal with this problem by using materials such as However, even when such bellows are used, after opening and closing millions of times, unlike in the past, problems may occur due to parts other than the bellows, which may lead to lifespan or vacuum breakdown. It turns out that there is. This problem is due to fatigue failure of the brazed part, which is caused by the structure of the vacuum valve. Specifically, it was found that there was a structural defect in the brazed part of the bellows cover and the movable shaft. It is something that

This conventional problem will be explained in more detail with reference to the drawings. FIG. 4 is a sectional view showing the vicinity of the attachment part of the bellows cover 7 of a conventional vacuum valve. In the following description, the same symbols will be used for parts equivalent to those described in FIG. 3.

As shown in FIG. 4, in the conventional vacuum valve, the central portion 8a of the bellows 8 and the central portion 7a of the bellows cover 7 are inserted into the movable shaft 6, engaged with the stepped portion 6a, and then joined by brazing. It consists of As shown in the figure, the brazing method involves placing ring-shaped brazing filler metals 10 in advance, heating them in a high-temperature furnace, and causing molten brazing filler metal 10 to flow between each component by capillary action. To do something.

However, the bellows cover 7 of this conventional vacuum valve is generally made of oxygen-free copper or stainless steel material with a thickness of about 1 to 2 mm, and is manufactured by press molding. As shown in b), there is a barrier b in the punched part of the central part 7a, albeit slightly.
and swell 7c were likely to occur. Therefore, when such parts are brazed, the barrier b and the canillary C impair the adhesion between the parts of the brazed part, that is, the brazed part between the bellows cover 7 and the bellows 8, which can lead to serious problems. I became afraid of being connected. This will be explained below. FIG. 6 is a sectional view showing a state where such a portion is brazed, taking barrier b as an example, and is shown in an exaggerated manner for convenience of explanation.

The shaded area indicated by 11 in the figure is the solder metal that has solidified. Here, the solder layer 11g filling the space between the bellows cover 7 and the bellows 8 is formed thickly as shown in the figure because the barrier b prevents the close contact between the two, and as a result, the solder layer 11g fills in the space between the bellows cover 7 and the bellows 8, and as a result, the solder layer 11g is formed thickly as shown in the figure. A concave portion 12 having a depressed shape may be formed in some cases.

To explain this solder layer 11a in detail, the thickness of the solder layer 11a in a state of close contact is usually on the order of 1/100 mm, but in these cases, the thickness is 0.2 to 0.3 mm. There is. Generally, when brazing, a suitable load is applied between the objects to be brazed to increase the adhesion between the two and to reduce the possibility of capillary action. In this case, the bellows cover 7 itself is 1 to 2 mm thick. , it is difficult to crush barrier b even if a normal load is applied. Therefore, when brazing is performed with the barrier b in between, the molten solder simply accumulates in the gap between the two members, and the concave portion 12 shrinks when cooled from the molten state at high temperature to room temperature. occurs, and at the same time wax layer 11
A large number of voids 13 are formed within a.

When the vacuum valve in which many voids 13 are formed in the brazing layer 11a is opened and closed, the vibration during opening and closing applies repeated bending stress to the bellows cover 7 using the brazed portion as a fulcrum. As a result of opening and closing millions of times, cracks occur starting from the concave portion 12, which is further promoted by the voids 13, and as a result, the bellows cover 7 peels off and falls off. Moreover, the vibration of the bellows cover 7 itself increases due to the partial peeling, and there is a risk of damaging the bellows 8 and causing a vacuum breakdown.

The present invention was made in view of the circumstances described above, and
The purpose is to provide a long-life vacuum valve with high reliability in opening and closing life.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a pair of electrodes arranged in an insulating container with a vacuum inside, a fixed shaft connected to one electrode, and a fixed shaft connected to the other electrode. is a vacuum valve to which a movable shaft is connected and which can be connected to and separated from one electrode in a vacuum-maintained state via a bellows.The movable shaft is integrally molded with a collar, and one end of the bellows is attached to one end of the collar. These are airtightly joined together.

(Function) A collar part that has the same function as a conventional bellows cover is integrally molded onto the movable shaft, and one end of the bellows is airtightly joined to one end surface of this collar part, making it easy to braze the bellows and the movable shaft. There are no harmful voids or recesses in the area.
It is possible to provide a vacuum valve with a long life and a highly reliable opening/closing life.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view showing essential parts of an embodiment of the present invention. The same structure as the conventional vacuum valve mentioned above is
The explanation will be omitted.

In FIG. 1, a movable shaft 14 connected to an electrode 4b and extending downward forms a radially extending collar portion 14a in the middle,
One end of the bellows 8 is engaged and brazed to the lower end surface 14b of the collar portion 14a, and is further extended downward and led out to the outside. Here, the diameter of the collar portion 14a is made approximately equal to the diameter of the conventional bellows cover 7.

In the above configuration, the lower end surface 14b of the collar portion 14B is
Precision can be easily achieved through machining. Therefore, unlike in the past, there are no burrs or undulations caused by press punching, so a thick brazing layer is not formed on the brazed portion of the bellows 8 and the lower end surface 14b of the collar 14g, unlike in the past. Concave areas and voids associated with the solder layer are eliminated.

That is, by adopting the above structure, the bellows cover 7 and the movable shaft 6 of the conventional vacuum valve explained in FIG. 7, it eliminates the need for brazing the bellows cover 7 and the movable shaft 6, which is difficult to achieve dimensional accuracy as in the past, and eliminates problems caused by this brazing.

The movable shaft 14 provided with the collar portion 14+ can be manufactured by a method such as forging.

Note that the present invention is not limited to the embodiments described above, and can be implemented in various modifications. FIG. 2 is a partial sectional view showing the main parts of another embodiment of the present invention.

In the figure, a movable shaft 1 connected to an electrode 4b and extending downward
5 has a collar portion 15g extending in the radial direction at the lower end;
A fitting hole 15c that opens in the lower end surface 15b is provided at the center of the collar 15a, and the connecting shaft 1 is provided in the hole 15c.
6 are joined by brazing. Further, one end of the bellows 8 is sandwiched between the joint shaft 16 and the lower end surface 25b of the collar portion 15g. Even with this arrangement, the same effects as in the embodiment shown in FIG. 1 can be obtained.

[Effects of the Invention] As explained above, according to the present invention, a thick solder layer, harmful voids, and concave portions of the solder layer do not occur after brazing (even if the solder layer is opened and closed many times). It is possible to prevent cracks from occurring in the soldered portion of the bellows and the movable shaft due to mechanical shock vibrations, and provide a vacuum valve with a long life and high reliability in opening and closing life.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing the main parts of one embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing the main parts of another embodiment of the present invention, and FIG. 3 is a cross-sectional view showing the conventional vacuum valve. Fig. 4 is an explanatory diagram showing the mounting structure of a conventional bellows cover, and Fig. 5 is an explanatory diagram showing the main part of the conventional bellows cover.
(b) shows the case where there is undulation, and FIG. 6 is an explanatory diagram showing an enlarged state of the conventional bellows cover after brazing. 0 2... Insulating container 4a, 4b... Electrode 5... Fixed shaft 8... Bellows 14... Movable shaft 14a... Collar portion

Claims (1)

[Claims] A pair of electrodes is arranged in an insulating container with a vacuum inside, a fixed shaft is connected to one electrode, a movable shaft is connected to the other electrode, and the electrode is connected to the above one electrode in a vacuum maintained state through a bellows. 1. A vacuum valve capable of being brought into and out of contact with the movable shaft, wherein the movable shaft is integrally molded with a collar portion, and one end of a bellows is hermetically joined to one end surface of the collar portion.